The invention relates to an optical disk library apparatus for selectively loading a plurality of optical disk medium cartridges enclosed in the apparatus into a drive and for recording or reproducing and, more particularly, to a very compact optical disk library apparatus which can be used when it is put on a desk.
An optical disk has advantages such as a large memory capacity exceeding 200 MB. Since it can be enclosed in a cartridge, a medium can be moved between different optical disk drives. In recent years, therefore, those advantages are being effectively used in a Windows environment and in an environment that uses a large amount of software. Particularly, in recent years, since the optical disk drive of 3.5 inches has been put into practical use, the reduction in costs and improvement in accessing speed are realized and a performance similar to that of a standard hard disk drive (HDD) of the previous generation is obtained. However, since the sole optical disk cartridge itself has a limitation in memory capacity, an optical disk library apparatus in which a plurality of optical disk cartridges are enclosed and a necessary optical disk cartridge is picked up by a robot hand and is loaded into the optical disk drive and therecording or reproducing is executed has been proposed.
Until now, a small desk-top optical disk library apparatus had a height almost equal to a height of a desk. The optical disk library apparatus can be installed under a desk and used as an external memory apparatus of a personal computer or a memory apparatus of a server machine. According to such a desk-top type optical disk library apparatus, a medium insertion/ejection port is provided in the outside of the apparatus and, when an optical disk cartridge is placed in the medium insertion/ejection port, an internal accessor conveys the cartridge to a designated cell of, for example, a rotatable cell drum and places it therein. When there is an access request from a host computer, the accessor picks up the cartridge in the cell on the moving side and conveys the cartridge to a drive on the movement destination side and loads it therein. The cartridge which was used is conveyed from the cell drum to the medium insertion/ejection port by the accessor and is ejected out of the apparatus.
In such a conventional desk-top type optical disk library apparatus, although 100 or more cartridges can be enclosed, due to an increase in memory capacity of the optical disk medium in recent years, assuming of the same memory capacity is required, the number of necessary cartridges remarkably decreases. For example, although the conventional optical disk of 3.5 inches has a memory capacity of about 100 MB, since the memory capacity has been increased to a value such as 230 MB which is two or more times larger than the conventional optical disk, the number of cartridges necessary for the optical disk library apparatus is reduced to half or less.
As mentioned above, in the case where the number of cartridges to be enclosed is reduced to, for example, 50 or less, the optical disk apparatus having a cell drum and a medium insertion/ejection port which are similar to those of the conventional apparatus has problems because the number of cartridges which can be enclosed is larger than the necessary number, and the mechanism structure that conveys cartridges between drives, cell drums, and insertion/ejection ports is complicated, expensive and large. As a result, it becomes difficult to find an adequate area to install the apparatus.
Further, in case of using the optical disk library apparatus as an external memory apparatus of a host computer, hitherto, input/output processes by an OS of the host computer have been formed for a hard disk as a target and it is not practical to prepare an OS according to the optical disk drive.
Therefore, hitherto, a hard disk emulation apparatus which operates by making the optical disk library apparatus look like a hard disk for an access from the host computer is used for the optical disk library apparatus as a target. In the conventional apparatus, therefore, an emulation format is fixedly set in accordance with the input/output processes for a hard disk prepared in the OS of the host computer.
In case of fixedly setting a hard disk emulation function, however, there is a situation such that it doesn't conform with specifications required by the user or a situation such that the library apparatus cannot be used due to a limitation or the like by the OS of the host computer which is connected. Since the optical disk library apparatus having the hard disk emulation function is made to look like a hard disk drive to the host computer, each medium cartridge cannot be managed. Consequently, problems can occur when the medium cartridge is taken out of the library apparatus for maintenance, etc. because the medium must be returned to its original format, which creates a high risk for errors.